The Gal/Ga1NAc reactive lectin associated with the type 2 fimbriae of the oral actinomyces mediates the adherence of these bacteria to a number of mammalian cells including erythrocytes, epithelial cells and polymorphonuclear leukocytes. On eukaryotic cells the galactose-containing receptors for the actinomyces lectin appears to be masked by sialic acid since bacterial attachment to these cells occurs only after treatment with sialidase, an enzyme secreted by the actinomyces. A 160 Kd cell surface sialoprotein on a human oral epithelial (KB) cell line has been identified as a putative receptor for the actinomyces. Analysis using Ga1/Ga1NAc specific plant lectins and a monoclonal antibody specific for Ga1Beta3Ga1NAc indicates that the 160Kd glycoprotein contains this carbohydrate sequence which is a potent inhibitor of actinomyces lectin mediated interactions. Certain glycolipids also contain the sequence Ga1Beta3Ga1NAc and we have recently shown that the actinomyces bind to gangliosides containing this sequence and to globoside which contains a terminal Ga1NAcBeta3Ga1. Our studies show that both glycoproteins and glycolipids may serve as receptors for the actinomyces lectin and studies are in progress to define and purify the glycoconjugates on eukaryotic cells which interact with the actinomyces.